Enabler of teaching pendant

ABSTRACT

In a case where a left-hand push-button switch is ON, a second relay RL 2  is electrically de-energized to open a normally close contact RL 2 - 1  of the second relay RL 2  so that a relay contact circuit RC is opened. If, in this state, a right-hand push-button switch is shifted to a second OFF state, a normally close contact R 3 - 1  of the right-hand push-button switch is opened. Thus, a third relay RL 3  is not electrically de-energized and a first and a second circuits are in cutoff until both the right-hand and the left-hand push-button switches are returned to a first OFF state.

TECHNICAL FIELD

[0001] The present invention relates to an enabler for teaching pendantwhich includes a push-button switch adapted to be shifted from a firstOFF state to an ON state as operatively associated with increasedpush-button depression and then to a second OFF state as operativelyassociated with further increased push-button depression.

BACKGROUND ART

[0002] In cases where, for example, a manual operation is performed onnumerically controlled machines such as robots, an operator often entersa dangerous area to carry out his job. In such cases, a pendant with apush-button switch, such as called an enable switch (or deadman switch),is used for obviating an accident associated with contact with any oneof operating machines during the execution of his job.

[0003] As shown in FIG. 30, a teaching pendant 101 includes a pendantbody 103, opposite end portions of which define grip portions 105 a, 105b to be held by respective hands, and which has a centrally locatedliquid crystal display (hereinafter referred to as “LCD”) 107. Asviewing a screen of the LCD 107, the operator may properly manipulate,with his thumbs or the like, a plural number of operation keys 109 a,109 b and other operation keys arranged along the opposite sides of theLCD 107, thereby teaching data, such as a program, to a robot orcontrolling the robot.

[0004] In this case, the teaching operation or the like to the robot isnot enabled by merely manipulating the operation keys 109 a, 109 b. Asshown in FIG. 31, an arrangement is made such that the robot is disabledfor program teaching or control unless operation sections 111 a, 111 bof a push-button switch (not shown) disposed on back sides of the gripportions of the pendant body 103 are manipulated to shift thepush-button switch to an ON state before the operation keys 109 a, 109 bare manipulated.

[0005] As shown in FIG. 32, a snap-action type push-button switch, forexample, may be used as such a push-button switch disposed at theteaching pendant.

[0006] As shown in FIG. 32, the push-button switch 113 includes a switchcase 115 having a rectangular shape in plan; a push button 117depressibly supported by the switch case 115; a normally close contact119, as an auxiliary contact, and a pair of c-contacts 121 a, 121 bdisposed in the switch case 115; and a pair of switching mechanisms 123a, 123 b disposed in the push button 117 and operatively associated withpressing-down on the push button 117 for switching the c-contacts 121 a,121 b between an open position and a close position.

[0007] The normally close contact 119 includes a movable member 127disposed within the switch case 115 as projecting toward the push button117 (upward) and urged upward by a helical spring 125 disposedthereunder; a pair of movable terminals 129 a, 129 b attached to themovable member 127; and a pair of stationary terminals 131 a, 131 badapted to be brought into or out of contact with the correspondingmovable terminals 129 a, 129 b. In an initial state, the movable member127 is urged upward by the helical spring 125, so that the normallyclose contact 119 is closed with the movable terminals 129 a, 129 bthereof contacting the stationary terminals 131 a, 131 b thereof.

[0008] The c-contacts 121 a, 121 b have a snap action configuration,individually including a movable terminal 133 a, 133 b; a normally closestationary terminal 135 a, 135 b and a normally open stationary terminal137 a, 137 b disposed above and below the movable terminal 133 a, 133 b,respectively; an operative member 139 a, 139 b for moving the movableterminal 133 a, 133 b between the normally close stationary terminal 135a, 135 b and the normally open stationary terminal 137 a, 137 b; and ahelical spring 141 a, 141 b anchored to the operative member 139 a, 139b and to the movable terminal 133 a, 133 b. When the c-contacts 121 a,121 b are in an initial state or in a first OFF state, the movableterminals 133 a, 133 b are in contact with the normally close stationaryterminals 135 a, 135 b, as spaced away from the normally open stationaryterminals 137 a, 137 b.

[0009] The switching mechanisms 123 a, 123 b are disposed in anaccommodating portion 143 defined in the push button 117. The switchingmechanisms 123 a, 123 b individually include a pressing piece 145 a, 145b for pressing the respective operative member 139 a, 139 b of thec-contact 121 a, 121 b; a slide block 147 a, 147 b for depressing therespective pressing piece 145 a, 145 b as operatively associated withpressing-down on the push button 117; and a pressing shaft 149 a, 149 bengaged with the respective slide block 147 a, 147 b.

[0010] The pressing shafts 149 a, 149 b are formed with a respectivepair of flanges 151 a, 151 b at a respective upper end thereof. Thepressing shafts 149 a, 149 b are formed with a slope 153 a, 153 b at oneof the flange pair 151 a, 151 b, respectively. The pressing shafts 149a, 149 b are of a hollow structure such that helical springs 155 a, 155b anchored to an upper inside surface of the accommodating portion 143are anchored to respective places within the pressing shafts 149 a, 149b.

[0011] The slide blocks 147 a, 147 b are individually formed with acavity 157 a, 157 b vertically extended therethrough, whereas thepressing shafts 149 a, 149 b are inserted through the cavities 157 a,157 b, respectively. The slide blocks 147 a, 147 b are individuallyformed with a slope 159 a, 159 b at an inside wall of one end thereof,the slopes 159 a, 159 b engaged with the corresponding slopes 153 a, 153b of the pressing shafts 149 a, 149 b. Helical springs 161 a, 161 b aredisposed in individual spaces between the one end of the slide block 147a and a side wall of the accommodating portion 143 and between the oneend of the slide block 147 b and the other side wall of theaccommodating portion 143. The helical springs 161 a, 161 b urge theslide blocks 147 a, 147 b toward the center of the push button 117. Therespective other end of the slide blocks 147 a, 147 b is adapted to bepressed against a respective upper end of the pressing pieces 145 a, 145b.

[0012] When the push button 117 of the push-button switch 113 in theinitial state shown in FIG. 32 or in the first OFF state is depressed,the pressing pieces 145 a, 145 b push down the operative members 139 a,139 b of the c-contacts 121 a, 121 b as operatively associated withpressing-down on the push button 117, thereby moving the movableterminals 133 a, 133 b away from the normally close stationary terminals135 a, 135 b and into contact with the normally open stationaryterminals 137 a, 137 b, as shown in FIG. 33. Thus, the push-buttonswitch 113 is shifted to an ON state.

[0013] When the push button 117 of the push-button switch 113 in the ONstate is further depressed, the slopes 159 a, 159 b of the slide blocks147 a, 147 b slide on the slopes 153 a, 153 b of the pressing shafts 149a, 149 b, so that the slide blocks 147 a, 147 b are moved outwardlyrelative to the pushbutton 117, as shown in FIG. 34. The movements ofthe slide blocks 147 a, 147 b release the individual other ends thereoffrom the engagement with the individual upper ends of the pressingpieces 145 a, 145 b which, in turn, are allowed to move upwardly torelease the pressure on the operative members 139 a, 139 b. This causesthe movable terminals 133 a, 133 b to move away from the normally openstationary terminals 137 a, 137 b and to come into contact with thenormally close stationary terminals 135 a, 135 b. Thus, the push-buttonswitch 113 in the ON state is shifted to a second OFF state.

[0014] That is, the push-button switch 113 permits key entry via theteaching pendant 101 only when the two c-contacts 121 a, 121 b are inthe ON state. Furthermore, the push-button switch 113 can be set to anyof three positions (the first OFF state, the ON state and the second OFFstate) according to the amounts of depression of the push button 117.Hence, the push-button switch provides for a tangible indication ofintent of the operator manually operating the machines, thus ensuringthe safety of the operator.

[0015] Next, an example of circuit connections of the teaching pendanthaving the above arrangement will be described with reference to FIG.35.

[0016] As shown in FIG. 35, the teaching pendant comprises threecircuits which include a first, a second and a third circuits. In thefirst circuit, one R1 of c-contacts of a right-hand push-button switchand one L1 of c-contacts of a left-hand push-button switch are connectedin parallel. In the second circuit, the other c-contact R2 of theright-hand push-button switch and the other c-contact L2 of theleft-hand push-button switch are connected in parallel. In the thirdcircuit, a normally close contact R3 of the right-hand push-buttonswitch and a normally close contact L3 of the left-hand push-buttonswitch are connected in series.

[0017] Based on such circuit connections, the teaching pendant 101 isenabled for data entry by way of either the right or left handmanipulating the push-button switch for driving the first and secondcircuits into conduction. Therefore, even in a case where the right handis fatigued by holding the operation section depressed in order toenable the program teaching, for example, the teaching pendant may bekept enabled for teaching by the left hand, in turn, which depresses theoperation section. In addition, the machines can be deactivated byeither the right or left hand manipulating the push-button switch toshift the push-button switch to the second OFF state. This leads to anenhanced safety of the operator who is carrying out his job.

[0018] It is noted here that NC1-R and NC2-R are equivalent to thenormally close stationary terminals 135 a, 135 b of the c-contacts R1,R2 (the same as the c-contacts 121 a, 121 b shown in FIG. 32, forexample) constituting the right-hand push-button switch; that NO1-R,NO2-R are equivalent to the normally open stationary terminals 137 a,137 b of the c-contacts 121 a, 121 b constituting the right-handpush-button switch; and that C1-R and C2-R are equivalent to the movableterminals 133 a, 133 b of the c-contacts R1, R2 constituting theright-hand push-button switch.

[0019] Likewise, NC1-L, NC2-L are equivalent to the normally closestationary terminals 135 a, 135 b of the c-contacts L1, L2 (the same asthe c-contacts 121 a, 121 b shown in FIG. 32, for example) constitutingthe left-hand push-button switch; NO1-L, NO2-L are equivalent to thenormally open stationary terminals 137 a, 137 b of the c-contacts L1, L2constituting the left-hand push-button switch; and C1-L and C2-L areequivalent to the movable terminals 133 a, 133 b of the c-contacts L1,L2 constituting the left-hand push-button switch. On the other hand, R3and L3 are each equivalent to the normally close contact 119constituting the right-hand or left-hand push-button switch.

[0020] In a case where the operator is aware of some potential dangerwhile performing the teaching operation via the teaching pendant withthe left-hand push-button switch held in the ON state, for example, itis also possible to deactivate the machines by driving the third circuitinto cutoff, as shown in FIG. 36, which is established by depressing theright-hand push-button switch to shift the same to the second OFF state.

[0021] In this case, if the pressure on the right-hand push-buttonswitch is released to return the same to the first OFF state while theleft-hand push-button switch is maintained in the ON state, as shown inFIG. 37, the first, second and third circuits are brought intoconduction again so that the left-hand push-button switch in the ONstate is active. Therefore, despite the right-hand push-button switchshifted to the second OFF state as emergency measure, the machines areso quickly enabled for teaching before both the push-button switches arereturned to the initial or first OFF state. Consequently, the teachingpendant suffers poor reliability.

[0022] It is an object of the present invention to provide an enablerfor teaching pendant which ensures that once either the right-hand orthe left-hand push-button switch is shifted to the second OFF state, theteaching pendant is never enabled before both the push-button switchesare shifted to the.first OFF state.

DISCLOSURE OF THE INVENTION

[0023] According to the present invention for achieving the aboveobject, an enabler for teaching pendant comprises a push-button switchcapable of being shifted from a first OFF state (undepressed) to an ONstate and then to a second OFF state as operatively associated withpush-button depressions and of establishing an enable state whenassuming the ON state, the enable state where a predetermined operationof an industrial machine is permitted, the enabler characterized in thatthe push-button switch comprises a switch case; a push buttondepressibly supported by the case; at least one primary contactincluding a stationary terminal disposed in the case, and a movableterminal shifted from an away position to a contact position and then tothe away position relative to the stationary terminal as operativelyassociated with pressing-down on the push button; and at least oneauxiliary contact disposed in the case and designed to be closed whenthe primary contact is in the first OFF state and to be opened when theprimary contact is in the second OFF state; that a left-hand operationsection to be gripped by the left hand and a right-hand operationsection to be gripped by the right hand are provided at a pendant body;that the push-button switches for left hand and for right hand aredisposed at individual inside portions of the both operation sections inorder to be manipulated by gripping; that the left-hand push-buttonswitch and the right-hand push-button switch are electrically connectedin a manner that the enable state is established by switching ON atleast either one of the left-hand push-button switch and the right-handpush-button switch; and that inhibition means is provided for inhibitingthe enable state for a period of time between when at least either oneof the left-hand push-button switch and the right-hand push-buttonswitch is shifted to the second OFF state and when both the left-handpush-button switch and the right-hand push-button switch are returned tothe first OFF state.

[0024] According to this arrangement, once either one of the push-buttonswitches is shifted to the second OFF state, the inhibition means caninhibit the enable state despite the ON state of the other push-buttonswitch until both the push-button switches are returned to the first OFFstate.

[0025] Therefore, even in a case where the left-hand push-button switchin the second OFF state is released to be returned to the ON state andthen to the first OFF state while the right-hand push-button switch ismaintained in the ON state, the enable state is never establisheddespite the right-hand push-button switch in the ON state. Thus, thesafety during operations can be enhanced.

[0026] In another aspect of the present invention, the enabler forteaching pendant is characterized in that the at least one primarycontact of the left-hand push-button switch is connected in parallelwith the at least one primary contact of the right-hand push-buttonswitch to form a parallel circuit; that the auxiliary contact of theleft-hand push-button switch is connected in series with the auxiliarycontact of the right-hand push-button switch to form a series circuit;and that the inhibition means comprises: a detection unit for detectingan open or close state of the parallel circuit and an open or closestate of the series circuit; and a retention unit for retaining theparallel circuit in the open state for a period of time between thedetection of the open state of the parallel circuit and the open stateof the series circuit, and the detection of the open state of theparallel circuit and the close state of the series circuit.

[0027] According to this arrangement, after the open state of both theparallel circuit and the series circuit is detected by the detectionunit, the retention unit maintains the parallel circuit in the openstate until the series circuit, with the open parallel circuit, isclosed. Therefore, in a case where with the left-hand push-button switchin the ON state or the parallel circuit in the close state, theright-hand push-button switch is shifted to the second OFF state therebyto open the parallel circuit and the series circuit, the enable state isnever established before both the push-button switches are released.Thus, the safety of the teaching pendant can be enhanced.

[0028] It is noted here that the detection unit may comprise a relaycircuit, or alternatively comprise an electronic circuit including aswitching element, such as a bipolar transistor or a unipolar transistorlike a field-effect transistor, and a control circuit for the switchingelement.

[0029] In another aspect of the present invention, the enabler forteaching pendant is characterized in that the left-hand and right-handpush-button switches include two of the primary contacts, respectively;that one of the primary contacts of the left-hand push-button switch isconnected in parallel with one of the primary contacts of the right-handpush-button switch to form a first parallel circuit; that the otherprimary contact of the left-hand push-button switch is connected inparallel with the other primary contact of the right-hand push-buttonswitch to form a second parallel circuit; that the auxiliary contact ofthe left-hand push-button switch is connected in series with theauxiliary contact of the right-hand push-button switch to form a seriescircuit; and that the inhibition means comprises: a first relay, a coilof which is electrically energized by switching ON the primary contactof the left-hand push-button switch in the first or second parallelcircuit; a second relay, a coil of which is electrically energized byswitching ON the primary contact of the right-hand push-button switch inthe first or second parallel circuit; a relay contact circuit having arespective normally close contact of the first and second relaysconnected in series, and connected in parallel with the series circuit;a third relay, a coil of which is electrically energized by switching ONthe both normally close contacts in the relay contact circuit; a firstnormally open contact of the third relay connected in series with theseries circuit; a second normally open contact of the third relayconnected in series with the primary contact of the left-handpush-button switch in the first or second parallel circuit, thus servingto conduct the coil of the first relay; a third normally open contact ofthe third relay connected in series with the primary contact of theright-hand push-button switch in the first or second parallel circuit,thus serving to conduct the coil of the second relay; and a fourthnormally open contact of the third relay connected in series with thesecond or first parallel circuit, not serving to conduct the coil of thefirst nor second relay.

[0030] According to this arrangement, in a case where the right-handpush-button switch is ON, for example, the second relay is electricallyde-energized to open the normally close contact thereof and hence, therelay contact circuit is opened. If, in this state, the left-handpush-button switch is shifted to the second OFF state, the auxiliarycontact of the left-hand push-button switch is opened. Accordingly, thethird relay is not electrically de-energized and the first and secondparallel circuits are cut off until both the right-hand and left-handpush-button switches are returned to the first OFF state.

[0031] Therefore, once either one of the push-button switches is shiftedto the second OFF state, the teaching pendant cannot be enabled despitethe ON state of the other push-button switch, before both thepush-button switches are returned to the first OFF state. Thus, thesafety of the teaching pendant can be enhanced.

[0032] In another aspect of the present invention, the enabler forteaching pendant is characterized in that the left-hand and right-handpush-button switches include two of the primary contacts, respectively;that one of the primary contacts of the left-hand push-button switch isconnected in parallel with one of the primary contacts of the right-handpush-button switch to form a first parallel circuit; that the otherprimary contact of the left-hand push-button switch is connected inparallel with the other primary contact of the right-hand push-buttonswitch to form a second parallel circuit; that the detection unitcomprises: a first relay, a coil of which is electrically energized byswitching ON the primary contact of the left-hand push-button switch inthe first or second parallel circuit; a second relay, a coil of which iselectrically energized by switching ON the primary contact of theright-hand push-button switch in the first or second parallel circuit; arelay contact circuit having a respective normally close contact of thefirst and second relays connected in series, and connected in parallelwith the series circuit; a third relay, a coil of which is electricallyenergized by switching ON the both normally close contacts in the relaycontact circuit; and a first normally open contact of the third relayconnected in series with the series circuit; and that the retention unitcomprises: a second normally open contact of the third relay connectedin series with the primary contact of the left-hand push-button switchin the first or second parallel circuit, thus serving to conduct thecoil of the first relay; a third normally open contact of the thirdrelay connected in series with the primary contact of the right-handpush-button switch in the first or second parallel circuit, thus servingto conduct the coil of the second relay; and a fourth normally opencontact of the third relay connected in series with the second or firstparallel circuit, not serving to conduct the coil of the first norsecond relay.

[0033] According to this arrangement, the detection unit comprises threerelays whereas the retention unit comprises the contacts adapted to beopened or closed by electrically energizing or de-energizing the relays.In a case where the right-hand push-button switch is ON, for example,the second relay is electrically de-energized to open the normally closecontact thereof and hence, the relay contact circuit is opened.

[0034] If, at this time, the left-hand push-button switch is shifted tothe second OFF state, the auxiliary contact of the left-hand push-buttonswitch is opened. Accordingly, the third relay is not electricallyde-energized and the first and second circuits are cut off until boththe right-hand and left-hand push-button switches are returned to thefirst OFF state.

[0035] Therefore, once either one of the push-button switches is shiftedto the second OFF state, the teaching pendant cannot be enabled despitethe ON state of the other push-button switch, before both thepush-button switches are returned to the first OFF state. Thus, thesafety of the teaching pendant can be enhanced.

[0036] In another aspect of the present invention, the enabler forteaching pendant is characterized in that the both push-button switcheseach comprise, as the auxiliary contact, a first auxiliary contact whichis closed when the both primary contacts are in the first OFF state andwhich is opened in the ON state and in the second OFF state, and asecond auxiliary contact which is closed when the both primary contactsare in the first OFF state and in the ON state and which is opened inthe second OFF state; that the at least one primary contact of theleft-hand push-button switch is connected in parallel with the at leastone primary contact of the right-hand push-button switch to form aparallel circuit; that the first auxiliary contact of the left-handpush-button switch is connected in series with the first auxiliarycontact of the right-hand push-button switch to form a first seriescircuit; that the second auxiliary contact of the left-hand push-buttonswitch is connected in series with the second auxiliary contact of theright-hand push-button switch to form a second series circuit; and thatthe inhibition means comprises: a detection unit for detecting an openor close state of the parallel circuit and an open or close state of thefirst or second series circuit; and a retention unit for retaining theparallel circuit in the open state for a period of time between when thedetection unit detects the open state of the parallel circuit and theopen state of the second series circuit, and when the detection unitdetects the open state of the parallel circuit and the close state ofthe first series circuit.

[0037] According to this arrangement, in a case where the right-handpush-button switch is ON, for example, the first auxiliary contact ofthe right-hand push-button switch is open so that the first seriescircuit is open. If, in this state, the left-hand push-button switch isshifted to the second OFF state, the second auxiliary contact of theleft-hand push-button switch is opened so that the second series circuitis opened. Accordingly, the retention unit maintains the parallelcircuit in the open state for disabling the teaching pendant to teachuntil the open state of the parallel circuit and the close state of thefirst series circuit are detected by the detection unit. Thus, thesafety of the teaching pendant can be enhanced.

[0038] It is noted here that the detection unit may comprise a relaycircuit, or alternatively comprise an electronic circuit including aswitching element, such as a bipolar transistor or a unipolar transistorlike a field-effect transistor, and a control circuit for the switchingelement.

[0039] In another aspect of the present invention, the enabler forteaching pendant is characterized in that the both push-button switcheseach comprise, as the auxiliary contact, a first auxiliary contact whichis closed when the both primary contacts are in the first OFF state andwhich is opened in the ON state and in the second OFF state, and asecond auxiliary contact which is closed when the both primary contactsare in the first OFF state and in the ON state and which is opened inthe second OFF state; that the at least one primary contact of theleft-hand push-button switch is connected in parallel with the at leastone primary contact of the right-hand push-button switch to form aparallel circuit; that the first auxiliary contact of the left-handpush-button switch is connected in series with the first auxiliarycontact of the right-hand push-button switch to form a first seriescircuit; that the second auxiliary contact of the left-hand push-buttonswitch is connected in series with the second auxiliary contact of theright-hand push-button switch to form a second series circuit which isconnected in parallel with the first series circuit; and that theinhibition means comprises: a fourth relay, a coil of which iselectrically energized by switching ON the both auxiliary contacts inthe first series circuit; a first normally open contact of the fourthrelay connected in series with the second series circuit; and a secondnormally open contact of the fourth relay connected in series with theparallel circuit.

[0040] According to this arrangement, in a case where the right-handpush-button switch is ON, for example, the first auxiliary contact ofthe right-hand push-button switch is open so that the first seriescircuit is open. If, in this state, the left-hand push-button switch isshifted to the second OFF state, the second auxiliary contact of theleft-hand push-button switch is opened so that the second series circuitis opened. Thus, the fourth relay is electrically de-energized to cutoff the parallel circuit.

[0041] Therefore, once either one of the push-button switches ismanually shifted to the second OFF state, the teaching pendant cannot beenabled despite the ON state of the other push-button switch, beforeboth the push-button switches are returned to the first OFF state. Thus,the safety of the teaching pendant can be enhanced.

[0042] In another aspect of the present invention, the enabler forteaching pendant is characterized in that the both push-button switcheseach comprise, as the auxiliary contact, a first auxiliary contact whichis closed when the both primary contacts are in the first OFF state andwhich is opened in the ON state and in the second OFF state, and asecond auxiliary contact which is closed when the both primary contactsare in the first OFF state and in the ON state and which is opened inthe second OFF state; that the at least one primary contact of theleft-hand push-button switch is connected in parallel with the at leastone primary contact of the right-hand push-button switch to form aparallel circuit; that the first auxiliary contact of the left-handpush-button switch is connected in series with the first auxiliarycontact of the right-hand push-button switch to form a first seriescircuit; that the second auxiliary contact of the left-hand push-buttonswitch is connected in series with the second auxiliary contact of theright-hand push-button switch to form a second series circuit which isconnected in parallel with the first series circuit; that the inhibitionmeans comprises: a fifth relay, a coil of which is electricallyenergized by switching ON the both auxiliary contacts in the firstseries circuit; and a normally open contact of the fifth relay connectedin series with the second series circuit, and that the parallel circuitis connected in series with the first series circuit.

[0043] According to this arrangement, in a case where the right-handpush-button switch is ON, for example, the first auxiliary contact ofthe right-hand push-button switch is open so that the first seriescircuit is open. If, in this state, the left-hand push-button switch isshifted to the second OFF state, the second auxiliary contact of theleft-hand push-button switch is opened to open the second seriescircuit. Thus, the parallel circuit connected with the first and secondseries circuits is cut off.

[0044] Therefore, once either one of the push-button switches ismanually shifted to the second OFF state, the teaching pendant cannot beenabled despite the ON state of the other push-button switch, beforeboth the push-button switches are returned to the first OFF state. Thus,the safety of the teaching pendant can be enhanced.

[0045] In another aspect of the present invention, the enabler forteaching pendant is characterized in that the both push-button switcheseach comprise, as the auxiliary contact, a first auxiliary contact whichis closed when the both primary contacts are in the first OFF state andwhich is opened in the ON state and in the second OFF state, and asecond auxiliary contact which is closed when the both primary contactsare in the first OFF state and in the ON state and which is opened inthe second OFF state; that the at least one primary contact of theleft-hand push-button switch is connected in parallel with the at leastone primary contact of the right-hand push-button switch to form aparallel circuit; that the first auxiliary contact of the left-handpush-button switch is connected in series with the first auxiliarycontact of the right-hand push-button switch to form a first seriescircuit; that the second auxiliary contact of the left-hand push-buttonswitch is connected in series with the second auxiliary contact of theright-hand push-button switch to form a second series circuit; that theinhibition means comprises a sixth relay including a normally opencontact and a c-contact, and a seventh relay including a normally opencontact and a c-contact; that the normally open contact of the sixthrelay and the normally open contact of the seventh relay are connectedin series with the parallel circuit; that a normally close terminal ofthe c-contact of the sixth relay and a normally close terminal of thec-contact of the seventh relay are connected to opposite ends of thefirst series circuit; and that a normally open terminal of the c-contactof the sixth relay and a normally open terminal of the c-contact of theseventh relay are connected to opposite ends of the second seriescircuit.

[0046] According to this arrangement, in a case where the right-handpush-button switch is ON, for example, the first auxiliary contact ofthe right-hand push-button switch is open so that the first seriescircuit is open. If, in this state, the left-hand push-button switch isshifted to the second OFF state, the second auxiliary contact of theleft-hand push-button switch is opened so that the second series circuitis opened. Thus, the sixth and seventh relays are electricallyde-energized to cut off the parallel circuit.

[0047] Therefore, once either one of the push-button switches ismanually shifted to the second OFF state, the teaching pendant cannot beenabled despite the ON state of the other push-button switch, beforeboth the push-button switches are returned to the first OFF state. Thus,the safety of the teaching pendant can be enhanced.

[0048] It is noted here that the c-contacts of the sixth and seventhrelays are connected to the first and second series circuits. Therefore,in the event that either one of the c-contacts is fused, the twoc-contacts are incapable of assuming the same open or close state eventhough both the push-button switches are returned to the first OFF statefrom the state where either one of the push-button switches is in thesecond OFF state. Accordingly, the sixth and seventh relays are notelectrically energized. This ensures that the teaching pendant cannot beenabled despite the ON state of the push-button switch, and alsofacilitates the detection of any failed contact.

[0049] In another aspect of the present invention, the enabler forteaching pendant is characterized in that the left-hand and theright-hand push-button switches include two of the primary contacts,respectively; that the both push-button switches each comprise, as theauxiliary contact, a first auxiliary contact which is closed when theboth primary contacts are in the first OFF state and which is opened inthe ON state and in the second OFF state, and a second auxiliary contactwhich is closed when the both primary contacts are in the first OFFstate and in the ON state and which is opened in the second OFF state;that one of the primary contacts of the left-hand push-button switch isconnected in parallel with one of the primary contacts of the right-handpush-button switch to form a first parallel circuit; that the other ofthe primary contacts of the left-hand push-button switch is connected inparallel with the other of the primary contacts of the right-handpush-button switch to form a second parallel circuit; that the firstauxiliary contact of the left-hand push-button switch is connected inseries with the first auxiliary contact of the right-hand push-buttonswitch to form a first series circuit; that the second auxiliary contactof the left-hand push-button switch is connected in series with thesecond auxiliary contact of the right-hand push-button switch to form asecond series circuit; that the inhibition means comprises an eighthrelay including a normally open contact and a c-contact, and a ninthrelay including a normally open contact and a c-contact; that either oneof the normally open contact of the eighth relay and the normally opencontact of the ninth relay is connected in series with the firstparallel circuit; that the remaining normally open contact of the eighthor ninth relay is connected in series with the second parallel circuit;that a normally close terminal of the c-contact of the eighth relay anda normally close terminal of the c-contact of the ninth relay areconnected to opposite ends of the first series circuit; and that anormally open terminal of the c-contact of the eighth relay and anormally open terminal of the c-contact of the ninth relay are connectedto opposite ends of the second series circuit.

[0050] According to this arrangement, in a case where the right-handpush-button switch is ON, for example, the first auxiliary contact ofthe right-hand push-button switch is open so that the first seriescircuit is open. If, in this state, the left-hand push-button switch isshifted to the second OFF state, the second auxiliary contact of theleft-hand push-button switch is opened so that the second series circuitis opened. Thus, the eighth and ninth relays are electricallyde-energized to cut off the first and second parallel circuits.

[0051] Therefore, once either one of the push-button switches ismanually shifted to the second OFF state, the teaching pendant cannot beenabled despite the ON state of the other push-button switch, beforeboth of the push-button switches are returned to the first OFF state.Thus, the safety of the teaching pendant can be enhanced.

[0052] In another aspect of the present invention, the enabler forteaching pendant is characterized in that the both push-button switcheseach comprise, as the auxiliary contact, a first auxiliary contact whichis closed when the both primary contacts are in the first OFF state andwhich is opened in the ON state and in the second OFF state, and asecond auxiliary contact which is closed when the both primary contactsare in the first OFF state and in the ON state and which is opened inthe second OFF state; that the at least one primary contact of theleft-hand push-button switch is connected in parallel with the at leastone primary contact of the right-hand push-button switch to form aparallel circuit; that the first auxiliary contact of the left-handpush-button switch is connected in series with the first auxiliarycontact of the right-hand push-button switch to form a first seriescircuit; that the second auxiliary contact of the left-hand push-buttonswitch is connected in series with the second auxiliary contact of theright-hand push-button switch to form a second series circuit; that theinhibition means comprises a tenth relay including a first and a secondnormally open contact and a normally close contact, the second normallyopen contact and the normally close contact of which are simultaneouslyswitched, and an eleventh relay including a first and a second normallyopen contact and a normally close contact, the second normally opencontact and the normally close contact of which are simultaneouslyswitched; that the first normally open contact of the tenth relay andthe first normally open contact of the eleventh relay are connected inseries with the parallel circuit; that the normally close contact of thetenth relay and the normally close contact of the eleventh relay areconnected in series with the first series circuit; and that the secondnormally open contact of the tenth relay and the second normally opencontact of the eleventh relay are connected in series with the secondseries circuit.

[0053] According to this arrangement, in a case where the right-handpush-button switch is ON, for example, the first auxiliary contact ofthe right-hand push-button switch is open so that the first seriescircuit is open. If, in this state, the left-hand push-button switch isshifted to the second OFF state, the second auxiliary contact of theleft-hand push-button switch is opened so that the second series circuitis opened. Thus, the tenth and eleventh relays are electricallyde-energized to cut off the parallel circuit.

[0054] Therefore, once either one of the push-button switches ismanually shifted to the second OFF state, the teaching pendant cannot beenabled regardless of the ON or OFF state of the other push-buttonswitch, before both the push-button switches are returned to the firstOFF state. Thus, the safety of the teaching pendant can be enhanced.

[0055] It is noted here that the second normally open contacts and thenormally close contacts of the tenth and eleventh relays are switchedsimultaneously. Therefore, in the event that any of the second normallyopen contacts and the normally close contacts is fused, the first andsecond series circuits are in different open/close states even thoughboth the push-button switches are returned to the first OFF state fromthe second OFF state. Accordingly, the tenth and eleventh relays are notelectrically energized. This ensures that the teaching pendant cannot beenabled despite the ON state of either one of the push-button switches,and also facilitates the detection of any failed contact.

[0056] In another aspect of the present invention, the enabler forteaching pendant is characterized in that the left-hand and theright-hand push-button switches include two of the primary contacts,respectively; that the both push-button switches each comprise, as theauxiliary contact, a first auxiliary contact which is closed when theboth primary contacts are in the first OFF state and which is opened inthe ON state and in the second OFF state, and a second auxiliary contactwhich is closed when the both primary contacts are in the first OFFstate and in the ON state and which is opened in the second OFF state;that one of the primary contacts of the left-hand push-button switch isconnected in parallel with one of the primary contacts of the right-handpush-button switch to form a first parallel circuit; that the other ofthe primary contacts of the left-hand push-button switch is connected inparallel with the other of the primary contacts of the right-handpush-button switch to form a second parallel circuit; that the firstauxiliary contact of the left-hand push-button switch is connected inseries with the first auxiliary contact of the right-hand push-buttonswitch to form a first series circuit; that the second auxiliary contactof the left-hand push-button switch is connected in series with thesecond auxiliary contact of the right-hand push-button switch to form asecond series circuit; that the inhibition means comprises a twelfthrelay including a first and a second normally open contact and anormally close contact, the second normally open contact and thenormally close contact of which are simultaneously switched, and athirteenth relay including a first and a second normally open contactand a normally close contact, the second normally open contact and thenormally close contact of which are simultaneously switched; that eitherone of the first normally open contact of the twelfth relay and thefirst normally open contact of the thirteenth relay is connected inseries with the first parallel circuit; that the remaining firstnormally open contact of the twelfth or thirteenth relay is connected inseries with the second parallel circuit; that the normally close contactof the twelfth relay and the normally close contact of the thirteenthrelay are connected in series with the first series circuit; and thatthe second normally open contact of the twelfth relay and the secondnormally open contact of the thirteenth relay are connected in serieswith the second series circuit.

[0057] According to this arrangement, in a case where the right-handpush-button switch is ON, for example, the first auxiliary contact ofthe right-hand push-button switch is open so that the first seriescircuit is open. If, in this state, the left-hand push-button switch isshifted to the second OFF state, the second auxiliary contact of theleft-hand push-button switch is opened so that the second series circuitis opened. Thus, the twelfth and thirteenth relays are electricallyde-energized to cut off the first and second parallel circuits.

[0058] Therefore, once either one of the push-button switches ismanually shifted to the second OFF state, the teaching pendant cannot beenabled regardless of the ON or OFF state of the other push-buttonswitch, before both the push-button switches are returned to the firstOFF state. Thus, the safety of the teaching pendant can be enhanced.

[0059] In another aspect of the present invention, the enabler forteaching pendant is characterized in that the relays or the detectionunit is disposed on a circuit substrate in the pendant body or in theswitch case of the left-hand or right-hand push-button switch. Accordingto this arrangement, the teaching pendant can be reduced in size becausethe relays or the detection unit is contained in the pendant body or theswitch case.

[0060] In an alternative arrangement, the relays or the detection unitmay be disposed in a relay box provided externally of the pendant body.For instance, a known relay module may be used for constructing theenabler for teaching pendant. In this case, the teaching pendant itselfhas a simple structure.

BRIEF DESCRIPTION OF THE DRAWINGS

[0061]FIG. 1 is a circuit connection diagram illustrative of operationsof a first embodiment of the present invention;

[0062]FIG. 2 is a circuit connection diagram illustrative of theoperations of the first embodiment hereof;

[0063]FIG. 3 is a circuit connection diagram illustrative of theoperations of the first embodiment hereof;

[0064]FIG. 4 is a circuit connection diagram illustrative of theoperations of the first embodiment hereof;

[0065]FIG. 5 is a sectional front elevation showing one state of apush-button switch according to a second embodiment of the presentinvention;

[0066]FIG. 6 is a sectional front elevation showing another state of thepush-button switch according to the second embodiment hereof;

[0067]FIG. 7 is a sectional front elevation showing still another stateof the push-button switch according to the second embodiment hereof;

[0068]FIG. 8 is a circuit connection diagram illustrative of operationsof the second embodiment hereof;

[0069]FIG. 9 is a circuit connection diagram illustrative of theoperations of the second embodiment hereof;

[0070]FIG. 10 is a circuit connection diagram illustrative of theoperations of the second embodiment hereof;

[0071]FIG. 11 is a circuit connection diagram illustrative of theoperations of the second embodiment hereof;

[0072]FIG. 12 is a diagram showing an exemplary modification of thecircuit connections of the second embodiment hereof;

[0073]FIG. 13 is a circuit connection diagram illustrative of operationsof a third embodiment of the present invention;

[0074]FIG. 14 is a circuit connection diagram illustrative of theoperations of the third embodiment hereof;

[0075]FIG. 15 is a circuit connection diagram illustrative of theoperations of the third embodiment hereof;

[0076]FIG. 16 is a circuit connection diagram illustrative of theoperations of the third embodiment hereof;

[0077]FIG. 17 is a circuit connection diagram illustrative of theoperations of the third embodiment hereof;

[0078]FIG. 18 is a circuit connection diagram illustrative of theoperations of the third embodiment hereof;

[0079]FIG. 19 is a diagram showing an exemplary modification of thecircuit connections of the third embodiment hereof;

[0080]FIG. 20 is a circuit connection diagram illustrative of operationsof a fourth embodiment of the present invention;

[0081]FIG. 21 is a circuit connection diagram illustrative of theoperations of the fourth embodiment hereof;

[0082]FIG. 22 is a circuit connection diagram illustrative of theoperations of the fourth embodiment hereof;

[0083]FIG. 23 is a circuit connection diagram illustrative of theoperations of the fourth embodiment hereof;

[0084]FIG. 24 is a circuit connection diagram illustrative of theoperations of the fourth embodiment hereof;

[0085]FIG. 25 is a circuit connection diagram illustrative of theoperations of the fourth embodiment hereof;

[0086]FIG. 26 is a diagram showing an exemplary modification of thecircuit connections of the fourth embodiment hereof;

[0087]FIG. 27 is a diagram showing circuit connections according to afifth embodiment of the present invention;

[0088]FIG. 28 is a diagram showing circuit connections according to asixth embodiment of the present invention;

[0089]FIG. 29 is a diagram showing circuit connections according to aseventh embodiment of the present invention;

[0090]FIG. 30 is a front elevation showing a conventional teachingpendant;

[0091]FIG. 31 is a perspective view of the conventional teaching pendantas seen from the rear side thereof;

[0092]FIG. 32 is a schematic diagram showing a construction of aconventional push-button switch;

[0093]FIG. 33 is a diagram illustrative of operations of theconventional push-button switch;

[0094]FIG. 34 is a diagram illustrative of the operations of theconventional push-button switch;

[0095]FIG. 35 is a diagram showing circuit connections of theconventional push-button switch;

[0096]FIG. 36 is a diagram showing the circuit connections of theconventional push-button switch; and

[0097]FIG. 37 is a diagram showing the circuit connections of theconventional push-button switch.

BEST MODES FOR CARRYING-OUT THE INVENTION

[0098] (First Embodiment)

[0099] A first embodiment of the present invention will be describedwith reference to FIGS. 1 to 4, which are circuit connection diagrams ofa teaching pendant. In the figures, the same reference characters asthose of the conventional example represent identical or equivalentparts to those of the conventional example, respectively.

[0100] Essential configurations of the teaching pendant of theembodiment and a push-button switch disposed therein are substantiallythe same as those of the conventional example shown in FIGS. 32 to 34.Therefore, the following description principally discusses differencesfrom the prior art referring to these figures as well, so that redundantdescriptions may be obviated. According to this embodiment, the teachingpendant has different circuit connections from those of the prior art.

[0101] As shown in FIG. 1, the teaching pendant comprises three circuitsincluding a first, a second and a third circuit, which are provided witha first relay RL1 and a second relay RL2 each including one normallyclose contact, and a third relay RL3 including four normally closecontacts. The first to third relays RL1 to RL3 are equivalent to a firstto third relays of the present invention, respectively.

[0102] In the first circuit, one R1 of c-contacts of a right-handpush-button switch is connected in parallel with one L1 of c-contacts ofa left-hand push-button switch to form a first parallel circuit. Thec-contact R1 is connected in series with a second normally open contactRL3-2 of the third relay RL3, whereas the c-contact L1 is connected inseries with a third normally open contact RL3-3 of the third relay RL3.In addition, the first relay RL1 is connected between the c-contact R1and the second normally open contact RL3-2 such that a coil of the firstrelay is electrically energized by switching ON the c-contact R1.Likewise, the second relay RL2 is connected between the c-contact L1 andthe third normally open contact RL3-3 such that the second relay iselectrically energized by switching ON the c-contact L1.

[0103] In the second circuit, the other c-contact R2 of the right-handpush-button switch is connected in parallel with the other c-contact L2of the left-hand push-button switch to form a second parallel circuit,which is connected in series with a fourth normally open contact RL3-4of the third relay RL3.

[0104] In the third circuit, a normally close contact R3 of theright-hand push-button switch, a normally close contact L3 of theleft-hand push-button switch, and a first normally open contact RL3-1 ofthe third relay RL3 are connected in series to form a series circuit SC.The series circuit SC is connected in parallel with a relay contactcircuit RC to form a third parallel circuit. The relay contact circuitRC includes a normally close contact RL1-1 of the first relay RL1 and anormally close contact RL2-1 of the second relay RL2 connected inseries. In addition, the third parallel circuit is connected in serieswith the third relay RL3, a coil of which is electrically energized byswitching ON both of the normally close contacts RL1-1, RL2-1 of therelay contact circuit RC.

[0105] Now referring to FIGS. 1 to 3, operations of the teaching pendantof the embodiment will be described.

[0106] When the left-hand push-button switch in an initial state(undepressed) shown in FIG. 1 is shifted to an ON state, the twoc-contacts L1, L2 of the left-hand push-button switch are switched ON.Hence, the c-contact L1 on one side electrically energizes the firstrelay RL1 and the second relay RL2, so that the normally close contactsRL1-1, RL2-1 of the first relay RL1 and the second relay RL2 in thethird circuit are switched OFF (opened), as shown in FIG. 2. This stateis an enable state for teaching operation wherein an operator is allowedto perform the teaching operation to an industrial machine such as anindustrial robot.

[0107] If, in this state, the operator being aware of any potentialdanger shifts the right-hand push-button switch to a second OFF state bydepressing the same, the normally close contact R3 of the right-handpush-button switch in the third circuit is switched OFF thereby drivingthe third circuit into cutoff, as shown in FIG. 3. Hence, the firstrelay RL1 and the third relay RL3 are electrically de-energized.Accordingly, the normally close contact RL1-1 of the first relay RL1 isreturned to the ON position (closed) whereas the first to fourthnormally open contacts RL3-1 to RL3-4 of the third relay RL3 areswitched OFF (opened) so that the first and second circuits are cut off.This brings the teaching pendant 101 into a disable state for teachingoperation.

[0108] In this case, if the right-hand push-button switch is returned tothe first OFF state by decreasing the pressure thereon while theleft-hand push-button switch is maintained in the ON state, as shown inFIG. 4, the relay contact circuit RC is out of conduction because thenormally close contact RL2-1 of the second relay is OFF. As a result,the third relay RL3 stays de-energized. Accordingly, the first andsecond circuits are maintained in cutoff, so that the ON position of theleft-hand push-button switch is disabled.

[0109] If, in this state, the left-hand push-button switch is returnedto the first OFF state by decreasing the pressure thereon, the first,second and third circuits are brought into conduction, as shown inFIG. 1. Hence, switching ON either of the push-button switches enablesthe teaching operation to the industrial machine such as the industrialrobot.

[0110] According to the first embodiment described above, the relaycontact circuit RC may be opened by switching ON the left-handpush-button switch, for example. If, in this state, the right-handpush-button switch is shifted to the second OFF state, the seriescircuit SC is opened so that the third relay is electricallyde-energized. This drives the first, second and third circuits intocutoff. Therefore, the left-hand push-button switch in the ON state canbe disabled even if the right-hand push-button switch in this state isshifted to the first OFF state by decreasing the pressure thereon.

[0111] That is, once either one of the push-button switches is shiftedto the second OFF state, the teaching pendant cannot be enabled forteaching operation before both of the push-button switches are returnedto the first OFF state. Thus, the safety of the teaching pendant can beenhanced.

[0112] According to the above embodiment, the circuit connections areimplemented using the push-button switches each employing two c-contactsbut the present invention is not limited to this. It goes without sayingthat an equivalent effect can be attained by the use of push-buttonswitches each employing one c-contact or three or more c-contacts.

[0113] The first embodiment described above employs the push-buttonswitches of the snap action configuration but the present invention isnot limited to this. For instance, push-button switches having a slowaction configuration may also be employed. In short, the push-buttonswitch may have any configuration that is adapted to be switched fromOFF to ON and then to OFF according to the increased press-down on thepush button.

[0114] (Second Embodiment)

[0115] A second embodiment of the present invention will be describedwith reference to FIGS. 5 to 11. FIGS. 5 to 7 are sectional frontelevations each illustrating operations of a push-button switch in eachdifferent state, whereas FIGS. 8 to 11 are diagrams each illustratingcircuit connections of a teaching pendant. In the figures, the samereference characters as those of the first embodiment described aboverepresent identical or equivalent parts to those of the firstembodiment, respectively.

[0116] In this embodiment, an essential configuration of the teachingpendant is substantially the same as that of the first embodiment andtherefore, the following description principally discusses differencesfrom the first embodiment so as to obviate redundant descriptions.

[0117] The teaching pendant of this embodiment differs from that of thefirst embodiment in the configuration of a push-button switch and acircuit connection configuration. In this embodiment, a rubber cover 2 aand an external button 2 b are mounted to a push button in a manner tocover the same for the purpose of improving the watertightness of thepush-button switch, as shown in FIG. 5. However, the rubber cover 2 a orthe external button 2 b is not necessarily provided.

[0118] As shown in FIG. 5, a push-button switch 1 is a three-positiontype switch which is adapted to be shifted from the first OFF state tothe ON state and then to the second OFF state according to the increasedpress-down on the push button. The push-button switch 1 comprises aswitch case 3 having a rectangular shape in plan; a push button 5depressibly supported by the switch case 3; two normally close contacts7 a, 7 b as auxiliary contacts and two c-contacts 121 a, 121 b disposedin the switch case 3; and a switching mechanism 9 disposed in the pushbutton 5 and operatively associated with pressing-down on the pushbutton 5 for switching the c-contacts 121 a, 121 b between an openposition and a close position.

[0119] As seen in the figure, the two normally close contacts or thefirst normally close contact 7 a and the second normally close contact 7b are located centrally downwardly of the switch case 3, whereas thepair of c-contacts 121 a, 121 b of the same configuration as in thefirst embodiment are disposed at opposite ends of the switch case assandwiching the normally close contacts therebetween.

[0120] The normally close contacts 7 a, 7 b individually include amovable member 13 a, 13 b disposed in the switch case 3 and projectingtoward the push button 5 (upwardly) as urged upward by a respectivehelical spring 11 a, 11 b disposed thereunder; a respective pair ofmovable terminals 15 a, 15 b attached to the movable member 13 a, 13 b;and a respective pair of stationary terminals 17 a, 17 b brought into orout of contact with the corresponding movable terminal 15 a, 15 b.

[0121] It is noted here that the movable member 13 a of the firstnormally close contact 7 a has a greater length than the movable member13 b of the second normally close contact 7 b. In this case, instead offorming the movable member 13 a of the first normally close contact 7 ain the greater length, a projection may be provided so as todifferentiate strokes of the movable member 13 a of the first normallyclose contact 7 a and the movable member 13 b of the second normallyclose contact 7 b. In an initial state, the movable members 13 a, 13 bare urged upward by the helical springs 11 a, 11 b so that the normallyclose contacts 7 a, 7 b are closed with the movable terminals 15 a, 15 bthereof contacting the stationary terminals 17 a, 17 b thereof.

[0122] The switching mechanism 9 comprises pressing pieces 19 a, 19 bfor individually depressing operative members 139 a, 139 b of thec-contacts 121 a, 121 b; a pair of slide blocks 21 a, 21 b operativelyassociated with pressing-down on the push button 5 for pushing down thepressing pieces 19 a, 19 b; and a pressing shaft 23 engaged with theslide blocks 21 a, 21 b.

[0123] The pressing pieces 19 a, 19 b have a respective lower endthereof pressed against a respective end of the operative members 139 a,139 b of the c-contacts 121 a, 121 b. The pressing shaft 23 is formedwith a pair of flanges 25 a, 25 b at an upper end thereof, the flanges25 a, 25 b each formed with a slope 27 a, 27 b at a lateral sidethereof. The pressing shaft 23 has a hollow structure, such that ahelical spring 29 anchored to an upper inside surface of the push button5 has its lower end anchored to place in the pressing shaft 23.

[0124] The slide blocks 21 a, 21 b individually define therein a cavityvertically extended therethrough, through which each drooping member 31a, 31 b is inserted. The drooping members 31 a, 31 b are located nearthe center of the push button 5. The slide blocks 21 a, 21 b arehorizontally movably disposed in a space defined by a pressure plate 33disposed in the push button 5 and the upper inside surface of the pushbutton 5. The slide blocks 21 a, 21 b are urged toward the center of thepush button 5 by means of helical springs 35 a, 35 b interposed betweena respective one end of the slide blocks 21 a, 21 b and the respectivedrooping member 31 a, 31 b.

[0125] The slide blocks 21 a, 21 b are formed with slopes 37 a, 37 b atthe respective one end thereof, the slopes 37 a, 37 b engaged with thecorresponding slopes 27 a, 27 b at the flanges 25 a, 25 b of thepressing shaft 23. The other ends of the slide blocks 21 a, 21 b areadapted to abut against upper ends of the pressing pieces 19 a, 19 b.

[0126] When the push button 5 of the push-button switch 1 in the initialstate or the first OFF state shown in FIG. 5 is depressed, the pressingpieces 19 a, 19 b are operatively associated with the pressing-down onthe push button 5 to push down the operative members 139 a, 139 b of thec-contacts 121 a, 121 b, as shown in FIG. 6. Hence, the movableterminals 133 a, 133 b are moved away from the normally close stationaryterminals 135 a, 135 b to come into contact with the normally openstationary terminals 137 a, 137 b, so that the push-button switch 1 isshifted to the ON state. At this time, the first normally close contact7 a is opened with the movable member 13 a thereof pushed down by thepressing plate 33. Therefore, the shift from the first OFF state to theON state of the push-button switch 1 can be determined by monitoring theopen/close state of the first normally close contact 7 a.

[0127] When the push button 5 of the push-button switch 1 in the ONstate is further depressed, the slopes 37 a, 37 b of the slide blocks 21a, 21 b slide on the slopes 27 a, 27 b of the pressing shaft 23 so thatthe slide blocks 21 a, 21 b are moved outwardly relative to the pushbutton 5, as shown in FIG. 7. The movement releases the abutmentrelation between the individual other ends of the slide blocks 21 a, 21b and the individual upper ends of the pressing pieces 19 a, 19 b.Hence, the pressing pieces 19 a, 19 b are moved upward to release thepressure on the operative members 139 a, 139 b so that the movableterminals 133 a, 133 b are moved away from the normally open stationaryterminals 137 a, 137 b to come into contact with the normally closestationary terminals 135 a, 135 b. Thus, the push-button switch 1 in theON state is shifted to the second OFF state.

[0128] At this time, the second normally close contact 7 b is openedwith the movable member 13 b thereof pushed down by the pressing plate33. Thus, that the shift from the ON state to the second OFF state ofthe push-button switch 1 can be determined by monitoring the open/closestate of the second normally close contact 7 b.

[0129] Next, description will be made on the circuit connections of theteaching pendant according to this embodiment.

[0130] As shown in FIG. 8, the teaching pendant comprises three circuitsincluding a first, a second and a third circuit, and a relay RLincluding three normally open contacts.

[0131] In the first circuit, one R1 of the c-contacts of the right-handpush-button switch is connected in parallel with one L1 of thec-contacts of the left-hand push-button switch to form a first parallelcircuit, which is connected in series with a first normally closecontact RL-1 of the relay RL.

[0132] In the second circuit, the other c-contact R2 of the right-handpush-button switch is connected in parallel with the other c-contact L2of the left-hand push-button switch to form a second parallel circuit,which is connected in series with a second normally close contact RL-2of the relay RL.

[0133] In the third circuit, a first normally close contact R3-1 of theright-hand push-button switch is connected in series with a firstnormally close contact L3-1 of the left-hand push-button switch to forma first series circuit, which is connected in parallel with a secondseries circuit wherein a second normally close contact R3-2 of theright-hand push-button switch, a second normally close contact L3-2 ofthe left-hand push-button switch and a third normally open contact ofthe relay RL are connected in series. The third circuit is connected inseries with the relay RL, a coil of which is electrically energized bythe close state of the first series circuit. It is noted here that R3-1and L3-1 represent the first normally close contact 7 a constituting theright-hand and the left-hand push-button switch, respectively, whereasR3-2 and L3-2 represent the second normally close contact 7 bconstituting the right-hand and the left-hand push-button switch,respectively. The relay RL is equivalent to a fourth relay of thepresent invention.

[0134] Next, operations of the teaching pendant according to theembodiment will be described with reference to FIGS. 8 to 11.

[0135] When the left-hand push-button switch in the initial state(undepressed) shown in FIG. 8 is shifted to the ON state, the twoc-contacts L1, L2 of the left-hand push-button switch are switched ONwhile the first normally close contact L3-1 is switched OFF (opened), asshown in FIG. 9. However, the relay RL of self-holding configuration iselectrically energized so that the first, second and third circuits aremaintained in conduction. Thus, the operator is allowed to perform theteaching operation to the industrial machine such as the industrialrobot.

[0136] If, in this state, the operator being aware of any potentialdanger shifts the right-hand push-button switch to the second OFF stateby depressing the same, the third circuit is cut off because the firstand second normally close contacts R3-1, R3-2 of the right-handpush-button switch in the third circuit are switched OFF, as shown inFIG. 10. Hence, the relay RL is electrically de-energized. Accordingly,the first to the third normally open contacts RL-1 to RL-3 of the relayRL are switched OFF so that the first and second circuits are cut off.Thus, the teaching pendant 101 is disabled for teaching operation.

[0137] In a case where, as shown in FIG. 11, the right-hand push-buttonswitch is returned to the first OFF state by decreasing the pressurethereon while the left-hand push-button switch is maintained in the ONstate, the first normally close contact R3-1 and the second normallyclose contact R3-2 of the right-hand push-button switch are sequentiallyswitched ON, but the third normally close contact RL-3 of the relay RLand the first normally close contact L3-1 of the left-hand push-buttonswitch are OFF. Hence, the third circuit is cutoff while the relay RLstays electrically de-energized. Accordingly, the first and secondcircuits are maintained in the cutoff state so that the left-handpush-button switch in the ON state is disabled.

[0138] If, in this state, the left-hand push-button switch is returnedto the first OFF state by decreasing the pressure thereon, the first,second and third circuits are brought into conduction, as shown in FIG.8. Thus, switching ON either of the push-button switches in this stateenables the teaching operation to the industrial machine such as theindustrial robot.

[0139] According to the second embodiment described above, the firstnormally close contact L3-1 of the left-hand push-button switch may beswitched OFF by shifting the left-hand push-button switch to the ONstate, for example. If, in this state, the right-hand push-button switchis shifted to the second OFF state, the two normally close contacts R3-1and R3-2 thereof are switched OFF. Therefore, the third circuit isopened so that the relay RL is electrically de-energized. This drivesthe first, second and third circuits into cutoff.

[0140] Accordingly, the left-hand push-button switch in the ON state isdisabled even though the right-hand push-button switch in the second OFFstate is returned to the first OFF state. Thus, the teaching pendant 101cannot be enabled for teaching operation before both of the push-buttonswitches are returned to the first OFF state. Thus, the safety of theteaching pendant 101 can be enhanced.

[0141] In the second embodiment described above, the first, the secondand the third circuits are independently provided. In an alternativeapproach as shown in FIG. 12, the teaching pendant 101 may have a singlecircuit configuration wherein the first and the second circuits inparallel connection are connected in series with the third circuit,whereas the first and the second normally open contacts of the relayconnected with the first and the second circuits are removed.

[0142] In such a single circuit configuration, once either one of thepush-button switches is shifted to the second OFF state, the thirdnormally close contact RL-3 of the relay RL is switched OFF therebydriving the first and the second parallel circuits into cutoff. As aresult, this single circuit configuration can naturally achieve the sameeffect as the above teaching pendant of the three circuit configuration.Furthermore, this circuit configuration reduces the number of normallyclose contacts of the relay, thus contributing to a simplified structureand cost reduction of the teaching pendant. The relay RL in this singlecircuit configuration is equivalent to a fifth relay of the presentinvention.

[0143] (Third Embodiment)

[0144] A third embodiment of the present invention will be describedwith reference to FIGS. 13 to 17, which are diagrams each illustratingcircuit connections of a teaching pendant. In the figures, the samereference characters as those of the second embodiment described aboverepresent identical or equivalent parts to those of the secondembodiment, respectively.

[0145] In this embodiment, an essential configuration of a push-buttonswitch is substantially the same as that of the second embodiment andhence, the following description principally discusses differences fromthe second embodiment so as to obviate redundant descriptions.

[0146] As shown in FIG. 13, the teaching pendant of this embodimentdiffers from the second embodiment in the circuit connections of thepush-button switch.

[0147] As shown in FIG. 13, the teaching pendant 101 comprises threecircuits including a first, a second and a third circuit, and a firstrelay RL1 and a second relay RL2 each including a first and secondnormally open contacts and a c-contact.

[0148] In the first circuit, one R1 of the c-contacts of the right-handpush-button switch is connected in parallel with one L1 of thec-contacts of the left-hand push-button switch to form a first parallelcircuit, opposite ends of which are connected in series with the firstnormally open contact RL1-1 of the first relay RL1 and the firstnormally open contact RL2-1 of the second relay RL2, respectively.

[0149] In the second circuit, the other c-contact R2 of the right-handpush-button switch is connected in parallel with the other c-contact L2of the left-hand push-button switch to form a second parallel circuit,opposite ends of which are connected in series with the second normallyopen contact RL1-2 of the first relay RL1 and the second normally opencontact RL2-2 of the second relay RL2, respectively.

[0150] The third circuit includes a first series circuit wherein thefirst normally close contact R3-1 of the right-hand push-button switchis connected in series with the first normally close contact L3-1 of theleft-hand push-button switch, and a second series circuit wherein thesecond normally close contact R3-2 of the right-hand push-button switchis connected in series with the second normally close contact L3-2 ofthe left-hand push-button switch. A normally close terminal of ac-contact RL1-3 of the first relay RL1 and a normally close terminal ofa c-contact RL2-3 of the second relay RL2 are connected with oppositeends of the first series circuit, respectively. On the other hand, anormally open terminal of the c-contact RL1-3 of the first relay RL1 anda normally open terminal of the c-contact RL2-3 of the second relay RL2are connected with opposite ends of the second series circuit,respectively. In the third circuit, the first relay RL1 and the secondrelay RL2 in parallel connection are connected in series with a commonterminal for the c-contact RL1-3 of the first relay RL1. It is notedhere that the first relay RL1 and the second relay RL2 are equivalent toa sixth relay and a seventh relay of the present invention.

[0151] In the initial state, the first relay RL1 and the second relayRL2 of the self-holding configuration are electrically energized so thatthe normally open contacts RL1-1, RL1-2, RL2-1, RL2-2 and the c-contactsRL1-3, RL2-3 of the relays RL1, RL2 are ON.

[0152] Next, operations of the teaching pendant of this embodiment willbe described with reference to FIGS. 13 to 16.

[0153] When the left-hand push-button switch in the initial state(undepressed) shown in FIG. 13 is shifted to the ON state, the twoc-contacts L1, L2 of the left-hand push-button switch are switched ONwhile the first normally close contact L3-1 thereof is switched OFF(opened), as shown in FIG. 14. However, the first relay RL1 and thesecond relay RL2 of the self-holding configuration are electricallyenergized so that the first, second and third circuits are maintained inconduction. Thus, the operator is allowed to perform the teachingoperation to the industrial machine such as the industrial robot.

[0154] If, in this state, the operator being aware of any potentialdanger shifts the right-hand push-button switch to the second OFF state,the third circuit is driven into cutoff because, as shown in FIG. 15,the first and second normally close contacts R3-1, R3-2 of theright-hand push-button switch in the third circuit are switched OFF.Hence, the first relay RL1 and the second relay RL2 are electricallyde-energized. Accordingly, the two normally open contacts RL1-1, RL1-2and the c-contact RL1-3 of the first relay RL1 and the two normally opencontacts RL2-1, RL2-2 and the c-contact RL2-3 of the second relay RL2are switched OFF so that the first and second circuits are cut off.Thus, the teaching pendant is disabled for teaching operation.

[0155] In a case where, as shown in FIG. 16, the right-hand push-buttonswitch is returned to the first OFF state by decreasing the pressurethereon while the left-hand push-button switch is maintained in the ONstate, the first normally close contact R3-1 and the second normallyclose contact R3-2 of the right-hand push-button switch are sequentiallyswitched ON, but the first normally close contact L3-1 of the left-handpush-button switch is OFF. Hence, the first and second relays RL1, RL2stay electrically de-energized so that the first and second circuits aremaintained in the cutoff state. Thus, the left-hand push-button switchin the ON state is disabled.

[0156] If, in this state, the left-hand push-button switch is returnedto the first OFF state by decreasing the pressure thereon, the first,second and third circuits are brought into conduction, as shown in FIG.13, wherein switching ON either of the push-button switches enables theteaching operation to the industrial machine such as the industrialrobot.

[0157] According to the third embodiment described above, the sameeffect as the second embodiment can naturally be obtained and inaddition, the following effect can also be attained.

[0158] In the event that the normally open contacts RL1-1, RL1-2 and thec-contact RL1-3 of the first relay RL1 are fused during the ON state ofthe left-hand push-button switch, for example, these contacts stay inthe ON state even though the first and second relays are electricallyde-energized by shifting the right-hand push-button switch to the secondOFF state, as shown in FIG. 17. At this time, however, the second relayRL2 is electrically de-energized so that the normally open contactsRL2-1, RL2-2 and the c-contact RL2-3 of the second relay RL2 are OFF.Thus, the first to third circuits are cut off. Accordingly, theleft-hand push-button switch in the ON state is disabled even if theright-hand push-button switch is returned to the first OFF state. Thus,the teaching pendant 101 is prevented from being enabled for teachingoperation.

[0159] If, in this state, both the left-hand and right-hand push-buttonswitches are returned to the first OFF state by decreasing the pressurethereon, the first relay RL1 and the second relay RL2 of theself-holding configuration are not electrically energized because thec-contact RL1-3 of the first relay RL1 is fused to stay in the ON state,as shown in FIG. 18. Hence, the c-contact RL2-3 of the second relay RL2is maintained in the OFF state, thus holding the third circuit in thecutoff state. Therefore, even if the push-button switch in this state ispressed ON, the teaching pendant 101 cannot be enabled for teachingoperation because of the disconnected third circuit.

[0160] In the event of either one of the relays suffering fusedcontacts, the above arrangement prevents the teaching pendant from beingenabled for teaching operation in spite of both the push-button switchesreturned to the first OFF state. Thus, the arrangement provides for aneasy determination of any failed contact, resulting in further enhancedsafety of the teaching pendant.

[0161] As shown in FIG. 19, an alternative arrangement may be made suchthat only one normally open contact is connected with the first circuitand the second circuit, respectively, whereas a disagreement detectionmodule is provided for detecting disagreement between open/closepositions of the first circuit and second circuits. This arrangement cannaturally obtain the same effect as the foregoing embodiments andbesides, permits the first and second circuits to be monitored for easydetection of disagreement in the open/close positions, or in otherwords, the occurrence of any fused contact in either of the circuits.Furthermore, the normally open contacts of the relays are decreased.

[0162] (Fourth Embodiment)

[0163] A fourth embodiment of the present invention will be describedwith reference to FIGS. 20 to 23, which are diagrams each showingcircuit connections of a teaching pendant. In the figures, the samereference characters as those of the second embodiment described aboverepresent identical or equivalent parts, respectively.

[0164] Since an essential configuration of a push-button switch of thisembodiment is substantially the same as that of the second embodiment,the following description principally discusses differences from thesecond embodiment so as to obviate redundant descriptions.

[0165] As shown in FIG. 20, a teaching pendant of this embodimentdiffers from that of the second embodiment in circuit connections of thepush-button switch.

[0166] Specifically, the teaching pendant comprises three circuitsincluding a first, a second and a third circuits, and a first relay RL1and a second relay RL2 each including a first, a second and a thirdnormally open contacts and a normally close contact.

[0167] In the first circuit, one R1 of c-contacts of a right-handpush-button switch is connected in parallel with one L1 of c-contacts ofa left-hand push-button switch to form a first parallel circuit, whichis connected in series with a first normally open contact RL1-1 of thefirst relay RL1 and a first normally open contact RL2-1 of the secondrelay RL2.

[0168] In the second circuit, the other c-contact R2 of the right-handpush-button switch is connected in parallel with the other c-contact L2of the left-hand push-button switch to form a second parallel circuit,which is connected in series with a second normally open contact RL1-2of the first relay RL1 and a second normally open contact RL2-2 of thesecond relay RL2.

[0169] The third circuit includes a first series circuit wherein a firstnormally close contact R3-1 of the right-hand push-button switch, afirst normally close contact L3-1 of the left-hand push-button switch, anormally close contact RL1-4 of the first relay RL1, and a normallyclose contact RL2-4 of the second relay RL2 are connected in series, anda second series circuit wherein a second normally close contact R3-2 ofthe right-hand push-button switch, a second normally close contact L3-2of the left-hand push-button switch, a third normally open contact RL1-3of the first relay RL1, and a third normally open contact RL2-3 of thesecond relay RL2 are connected in series. The first series circuit andthe second series circuit are connected in parallel. The first relay RL1and the second relay RL2 in parallel connection are connected in serieswith the third circuit.

[0170] It is noted here that the third normally open contacts RL1-3,RL2-3 and the normally close contacts RL1-4, RL2-4 of the first andsecond relays RL1, RL2 are of a so-called forcefully guided relayconfiguration for simultaneous switch ON/OFF. For instance, whenever thethird normally open contact RL1-3 of the first relay RL1 is switched ON,the normally close contact RL1-4 thereof is switched OFF.

[0171] In an initial state (where the push-button switches areundepressed), the first and second relays RL1, RL2 of the self-holdingconfiguration are electrically energized so that the normally opencontacts RL1-1 to RL1-3, RL2-1 to RL2-3 of the relays RL1, RL2 are ONwhile the normally close contacts RL1-4, RL2-4 are OFF. It is noted thatthe first relay RL1 and the second relay RL2 of this embodiment areequivalent to a tenth relay and an eleventh relay of the presentinvention.

[0172] Now referring to FIGS. 20 to 23, operations of the teachingpendant of this embodiment will be described.

[0173] When the left-hand push-button switch in the initial state(undepressed) shown in FIG. 20 is shifted to the ON state, the twoc-contacts L1, L2 of the left-hand push-button switch are switched ONwhile the first normally close contact L3-1 thereof is switched OFF, asshown in FIG. 21. However, the first, second and third circuits aremaintained in conduction because the first relay RL1 and the secondrelay RL2 of the self-holding configuration are electrically energized.Thus, the operator is allowed to perform the teaching operation to theindustrial machine such as the industrial robot.

[0174] If, in this state, the operator being aware of any potentialdanger shifts the right-hand push-button switch to the second OFF state,the third circuit is driven into cutoff because the first and secondnormally close contacts R3-1, R3-2 of the right-hand push-button switchin the third circuit are switched OFF, as shown in FIG. 22. Hence, thefirst relay RL1 and the second relay RL2 are electrically de-energized.Accordingly, the three normally open contacts RL1-1, RL1-2, RL1-3 of thefirst relay RL1 and the three normally open contacts RL2-1, RL2-2, RL2-3of the second relay RL2 are switched OFF so that the first and secondcircuits are driven into cutoff. Thus, the teaching pendant 101 isdisabled for teaching operation.

[0175] In a case where, as shown in FIG. 23, the right-hand push-buttonswitch is returned to the first OFF state by decreasing the pressurethereon while the left-hand push-button switch is maintained in the ONstate, the first normally close contact R3-1 and the second normallyclose contact R3-2 of the right-hand push-button switch are sequentiallyswitched ON, but the first normally close contact L3-1 of the left-handpush-button switch as well as the third normally open contact RL1-3 ofthe first relay RL1 and the third normally open contact RL2-3 of thesecond relay RL2 are OFF. Hence, the first and second relays RL1, RL2stay electrically de-energized. As a result, the first and secondcircuits are maintained in the cutoff state so that the left-handpush-button switch in the ON state is disabled.

[0176] If, in this state, the left-hand push-button switch is returnedto the first OFF state by decreasing the pressure thereon, the first,second and third circuits are brought into conduction, as shown in FIG.20, wherein switching ON either of the push-button switches enables theteaching operation to the industrial machine such as the industrialrobot.

[0177] According to the fourth embodiment described above, the sameeffect as the second embodiment can naturally be obtained and inaddition, the following effect can also be attained.

[0178] In the event that the normally open contacts RL1-1 to RL1-3 andthe normally close contact RL1-4 of the first relay RL1 are fused duringthe ON state of the left-hand push-button switch, for example, thenormally close contacts RL1-1 to RL1-3 of the first relay RL1 stay inthe ON state while the normally close contact RL1-4 thereof stay in theOFF state even though the first and second relays RL1, RL2 areelectrically de-energized by shifting the right-hand push-button switchto the second OFF state, as shown in FIG. 24. At this time, however, thenormally open contacts RL2-1 to RL2-3 of the second relay RL2 are OFF sothat the first to third circuits are cut off. Accordingly, the left-handpush-button switch in the ON state is disabled even though theright-hand push-button switch in this state is returned to the first OFFstate. Thus, the teaching pendant 101 is prevented from being enabledfor teaching operation.

[0179] If, in this state, both the left-hand and right-hand push-buttonswitches are returned to the first OFF state, the first and the secondseries circuits of the third circuit are opened, as shown in FIG. 25.Hence, the first relay RL1 and the second relay RL2 cannot effect theself-holding function so that the third circuit stays in the cutoffstate. Accordingly, even if either of the push-button switches in thisstate is pressed ON, the teaching pendant cannot be enabled for teachingoperation because of the disconnected third circuit.

[0180] In the event of either one of the relays suffering any fusedcontact, the above arrangement prevents the teaching pendant from beingenabled for teaching operation in spite of both the push-button switchesreturned to the first OFF state. Thus, this arrangement provides for aneasy determination of any failed contacts, resulting in further enhancedsafety of the teaching pendant.

[0181] As shown in FIG. 26, an alternative arrangement may be made suchthat only one normally open contact is connected with the first circuitand the second circuit, respectively, whereas a disagreement detectionmodule is provided for detecting disagreement between open/closepositions of the first and second circuits. This arrangement cannaturally obtain the same effect as the foregoing embodiments andbesides, permits the first and second circuits to be monitored for easydetection of disagreement in the open/close positions, or in otherwords, the occurrence of any fused contact in either of the circuits.Furthermore, the normally open contacts of the relays are decreased.

[0182] (Fifth Embodiment)

[0183] A fifth embodiment of the present invention will be describedwith reference to FIG. 27, which is a diagram showing circuitconnections between push-button switches of a teaching pendant and asafety relay module. In the figure, the same reference characters asthose of the fourth embodiment described above represent identical orequivalent parts, respectively.

[0184] Since an essential configuration of the push-button switch ofthis embodiment is substantially the same as that of the fourthembodiment described above, the following description principallydiscusses differences from the fourth embodiment so as to obviateredundant descriptions.

[0185] As shown in FIG. 27, this embodiment employs a safety relaymodule as means for controlling the enable state of the teachingpendant, the safety relay module comprising a relay box disposedexternally of the teaching pendant. Specifically, the fourth embodimentdescribed above has the arrangement wherein the teaching pendantcontains therein the relay circuit for controlling the enable statethereof, whereas this embodiment does not contain therein the relaycircuit but employs the external safety module.

[0186] As shown in FIG. 27, an enabler for the teaching pendant has anarrangement wherein both a first series circuit and a second seriescircuit are connected with a positive line (+) at respective one endthereof, and are connected with a safety relay module RM at therespective other end thereof. The first series circuit includes a firstnormally close contact R3-1 of a right-hand push-button switch and afirst normally close contact L3-1 of a left-hand push-button switchconnected in series. The second series circuit includes a secondnormally close contact R3-2 of the right-hand push-button switch and asecond normally close contact L3-2 of the left-hand push-button switchconnected in series.

[0187] Further, the safety relay module RM is connected with oppositeends of a first parallel circuit wherein one R1 of c-contacts of theright-hand push-button switch is connected in parallel with one L1 ofc-contacts of the left-hand push-button switch, and with opposite endsof a second parallel circuit wherein the other c-contact R2 of theright-hand push-button switch is connected in parallel with the otherc-contact L2 of the left-hand push-button switch. Incidentally, thesafety relay module RM is connected to a negative line (−).

[0188] The safety relay module RM contains therein a relay circuithaving substantially the same forcefully guided relay and relay contactsas those of the fourth embodiment described above. For example, thesafety relay module is normally used for checking safety operations of ateaching pendant or emergency switch, or for checking operations ofother circuits.

[0189] Using the known safety relay module RM, this embodiment cannaturally achieve the equal effect to that of the fourth embodimentdescribed above. In addition, this embodiment provides simplifiedcircuit connections in the teaching pendant, facilitating maintenancework for the teaching pendant.

[0190] (Sixth Embodiment)

[0191] A sixth embodiment of the present invention will be describedwith reference to FIG. 28, which is a diagram showing circuitconnections of a teaching pendant. In the figure, the same referencecharacters as those of the first embodiment described above representidentical or equivalent parts, respectively.

[0192] Since an essential configuration of a push-button switch of thisembodiment is substantially the same as that of the first embodiment,the following description principally discusses differences from thefirst embodiment so as to obviate redundant descriptions.

[0193] As shown in FIG. 28, the teaching pendant has substantially thesame configuration as the first embodiment that includes the first,second and third circuits, which are controlled by a detection unit DT,a control unit CO and an operation unit OP which each compriseelectronic circuits.

[0194] In the first circuit, one R1 of c-contacts of a right-handpush-button switch is connected in parallel with one L1 of c-contacts ofa left-hand push-button switch to form a first parallel circuit. In thesecond circuit, the other c-contact R2 of the right-hand push-buttonswitch is connected in parallel with the other c-contact L2 of theleft-hand push-button switch to form a second parallel circuit. In thethird circuit, a normally close contact R3 of the right-hand push-buttonswitch is connected in series with a normally close contact L3 of theleft-hand push-button switch.

[0195] Circuit connections of the first and second parallel circuits areprovided with the operation unit OP for operatively opening or closingthese circuits. The first, second and third circuits are connected inseries with the detection unit DT for detecting the open or close statesof these circuits.

[0196] The open or close states of the first to third circuits sodetected by the detection unit DT are inputted to the control unit COwhich, in turn, controls the operation unit OP for effecting the similarcontrol provided by the relay circuit of the first embodiment describedabove.

[0197] The operation unit OP may employ a switching element such as abipolar transistor or a unipolar transistor like a field-effecttransistor.

[0198] Thus as with the first embodiment, the sixth embodiment ensuresthat once either one of the push-button switches is manually shifted tothe second OFF state, the teaching pendant cannot be enabled forteaching operation despite the ON state of the other push-button switchbefore both the push-button switches are returned to the first OFFstate.

[0199] In addition, the enabler comprises the electronic circuits which,unlike the relay circuit, are free from the fear of contacts becomingfused. Thus, the embodiment provides a unique effect to ensure positiveoperations.

[0200] (Seventh Embodiment)

[0201] A seventh embodiment of the present invention will be describedwith reference to FIG. 29, which is a diagram showing circuitconnections of a teaching pendant. In the figure, the same referencecharacters as those of the second embodiment described above representidentical or equivalent parts, respectively.

[0202] In this embodiment, an essential configuration of a push-buttonswitch is substantially the same as that of the second embodiment andhence, the following description principally discusses differences fromthe second embodiment so as to obviate redundant descriptions.

[0203] As shown in FIG. 29, the teaching pendant has substantially thesame configuration as that of the second embodiment that includes thefirst, second and third circuits, which are controlled by a detectionunit DT, a control unit CO and an operation unit OP which each compriseelectronic circuits.

[0204] In the first circuit, one R1 of c-contacts of a right-handpush-button switch is connected in parallel with one L1 of c-contacts ofa left-hand push-button switch to form a first parallel circuit. In thesecond circuit, the other c-contact R2 of the right-hand push-buttonswitch is connected in parallel with the other c-contact L2 of theleft-hand push-button switch to form a second parallel circuit. In thethird circuit, a first series circuit and a second series circuit areconnected in parallel, the first series circuit wherein a first normallyclose contact R3-1 of the right-hand push-button switch is connected inseries with a first normally close contact L3-1 of the left-handpush-button switch, the second series circuit wherein a second normallyclose contact R3-2 of the right-hand push-button switch is connected inseries with a second normally close contact L3-2 of the left-handpush-button switch.

[0205] Circuit connections of the first and second parallel circuits areprovided with the operation unit OP for operatively opening or closingthese circuits. The first, second and third circuits are connected inseries with the detection unit DT for detecting the open or close statesof these circuits.

[0206] The open or close states of the first to third circuits sodetected by the detection unit DT are inputted to the control unit COwhich, in turn, controls the operation unit OP for effecting the similarcontrol provided by the relay circuit of the second embodiment (and thethird and fourth embodiments).

[0207] Similarly to the sixth embodiment, the operation unit OP maypreferably employ a switching element such as a bipolar transistor or aunipolar transistor like a field-effect transistor.

[0208] Thus as with the second embodiment, the seventh embodimentensures that once either one of the push-button switches is manuallyshifted to the second OFF state, the teaching pendant cannot be enabledfor teaching operation despite the ON state of the other push-buttonswitch before both the push-button switches are returned to the firstOFF state.

[0209] In this case as well, the enabler comprises the electroniccircuits which, unlike the relay circuit, are free from the fear ofcontacts becoming fused. Thus, the embodiment provides a unique effectto ensure positive operations.

[0210] Although the foregoing embodiments employ the push-buttonswitches of the snap action configuration, a push-button switch of aso-called slow action configuration may be used. A specific applicableconfiguration of the primary contact of the slow-action type switch maybe exemplified by a configuration shown in FIG. 38 accompanying adescription of Japanese Patent Application No. 2000-232229 filed by thepresent applicant.

[0211] The foregoing embodiments illustrate the double-safetyconfiguration based on the two parallel circuits as the safety measure.However, the provision of a single parallel circuit may serve theprinciple of operation of the present invention.

[0212] In addition, modification may properly be made to each of theforegoing embodiments such that the normally close contact of the relayis replaced by the normally open contact or vise versa as required toobtain an equivalent operation or working effect to that of each of theforegoing embodiments.

[0213] It is to be understood that the present invention is not limitedto the foregoing embodiments and various other changes and modificationsmay be made thereto within the scope of the present invention.

[0214] Industrial Applicability

[0215] As mentioned supra, the enabler for teaching pendant according tothe present invention ensures that once either one of the push-buttonswitches is shifted to the second OFF state, the inhibition meansinhibits the enable state despite the ON state of the other push-buttonswitch until both the push-button switches are shifted to the first OFFstate. Thus, the safety during operations can be enhanced.

[0216] Furthermore, the enabler for teaching pendant according to thepresent invention is arranged such that after the detection unit hasdetermined both the parallel circuit and the series circuit to beopened, the retention unit holds the parallel circuit in the open stateuntil the series circuit is closed with the parallel circuit opened.Accordingly, in a case, for example, where the left-hand push-buttonswitch is in the ON state or the parallel circuit is closed, despite theright-hand push-button switch shifted to the second OFF state where theparallel circuit and the series circuit are opened, the enable state isnever established before both of the push-button switches are released.Thus, the teaching pendant can be enhanced in safety feature.

[0217] In addition, the enabler for teaching pendant according to thepresent invention ensures that once either one of the push-buttonswitches is shifted to the second OFF state, the enable state cannot beestablished despite the ON state of the other push-button switch beforeboth the push-button switches are returned to the first OFF state. Thus,the teaching pendant can be enhanced in safety feature.

[0218] In a case where the right-hand push-button switch is ON, forexample, the second relay is electrically de-energized to open thenormally close contact thereof, so that the relay contact circuit isopened. If, at this time, the left-hand push-button switch is shifted tothe second OFF state, the auxiliary contact of the left-hand push-buttonswitch is opened.

[0219] Therefore, before both the right-hand and the left-handpush-button switches are returned to the first OFF state, the thirdrelay is not electrically de-energized while the first and secondcircuits are cut off. Thus, once either one of the push-button switchesis shifted to the second OFF state, the enable state cannot beestablished despite the ON state of the other push-button switch, beforeboth the push-button switches are returned to the first OFF state. Thus,the teaching pendant can be enhanced in safety feature.

1. An enabler for teaching pendant comprising a push-button switchcapable of being shifted from a first OFF state (undepressed) to an ONstate and then to a second OFF state as operatively associated withpush-button depressions and of establishing an enable state whenassuming said ON state, the enable state where a predetermined operationof an industrial machine is permitted; wherein said push-button switchcomprises a switch case; a push button depressibly supported by saidcase; at least one primary contact including a stationary terminaldisposed in said case, and a movable terminal shifted from an awayposition to a contact position and then to the away position relative tosaid stationary terminal as operatively associated with pressing-down onsaid push button; and at least one auxiliary contact disposed in saidcase and designed to be closed when said primary contact is in saidfirst OFF state and to be opened when said primary contact is in saidsecond OFF state; wherein a left-hand operation section to be gripped bythe left hand and a right-hand operation section to be gripped by theright hand are provided at a pendant body; wherein said push-buttonswitches for left hand and for right hand are disposed at individualinside portions of said both operation sections in order to bemanipulated by gripping; wherein said left-hand push-button switch andsaid right-hand push-button switch are electrically connected in amanner that the enable state is established by switching ON at leasteither one of said left-hand push-button switch and said right-handpush-button switch; and wherein inhibition means is provided forinhibiting the enable state for a period of time between when at leasteither one of said left-hand push-button switch and said right-handpush-button switch is shifted to said second OFF state and when bothsaid left-hand push-button switch and said right-hand push-button switchare returned to said first OFF state.
 2. The enabler for teachingpendant as claimed in claim 1, wherein said at least one primary contactof said left-hand push-button switch is connected in parallel with saidat least one primary contact of said right-hand push-button switch toform a parallel circuit; wherein said auxiliary contact of saidleft-hand push-button switch is connected in series with said auxiliarycontact of said right-hand push-button switch to form a series circuit;and wherein said inhibition means comprises: a detection unit fordetecting an open or close state of said parallel circuit and an open orclose state of said series circuit; and a retention unit for retainingsaid parallel circuit in the open state for a period of time betweenwhen said detection unit detects the open state of said parallel circuitand the open state of said series circuit, and when said detection unitdetects the open state of said parallel circuit and the close state ofsaid series circuit.
 3. The enabler for teaching pendant as claimed inclaim 1, wherein said left-hand and right-hand push-button switchesinclude two of said primary contacts, respectively; wherein one of saidprimary contacts of said left-hand push-button switch is connected inparallel with one of said primary contacts of said right-handpush-button switch to form a first parallel circuit; wherein the otherof said primary contacts of said left-hand push-button switch isconnected in parallel with the other of said primary contacts of saidright-hand push-button switch to form a second parallel circuit; whereinsaid auxiliary contact of said left-hand push-button switch is connectedin series with said auxiliary contact of said right-hand push-buttonswitch to form a series circuit; and wherein said inhibition meanscomprises: a first relay, a coil of which is electrically energized byswitching ON said primary contact of said left-hand push-button switchin said first or second parallel circuit; a second relay, a coil ofwhich is electrically energized by switching ON said primary contact ofsaid right-hand push-button switch in said first or second parallelcircuit; a relay contact circuit having a respective normally closecontact of said first and second relays connected in series, andconnected in parallel with said series circuit; a third relay, a coil ofwhich is electrically energized by switching ON said both normally closecontacts in said relay contact circuit; a first normally open contact ofsaid third relay connected in series with said series circuit; a secondnormally open contact of said third relay connected in series with saidprimary contact of said left-hand push-button switch in said first orsecond parallel circuit, thus serving to conduct the coil of said firstrelay; a third normally open contact of said third relay connected inseries with said primary contact of said right-hand push-button switchin said first or second parallel circuit, thus serving to conduct thecoil of said second relay; and a fourth normally open contact of saidthird relay connected in series with said second or first parallelcircuit, not serving to conduct the coil of said first nor second relay.4. The enabler for teaching pendant as claimed in claim 2, wherein saidleft-hand and right-hand push-button switches include two of saidprimary contacts, respectively; wherein one of said primary contacts ofsaid left-hand push-button switch is connected in parallel with one ofsaid primary contacts of said right-hand push-button switch to form-afirst parallel circuit; wherein the other of said primary contacts ofsaid left-hand push-button switch is connected in parallel with theother of said primary contacts of said right-hand push-button switch toform a second parallel circuit; wherein said detection unit comprises: afirst relay, a coil of which is electrically energized by switching ONsaid primary contact of said left-hand push-button switch in said firstor second parallel circuit; a second relay, a coil of which iselectrically energized by switching ON said primary contact of saidright-hand push-button switch in said first or second parallel circuit;a relay contact circuit having a respective normally close contact ofsaid first and second relays connected in series, and connected inparallel with said series circuit; a third relay, a coil of which iselectrically energized by switching ON said both normally close contactsin said relay contact circuit; and a first normally open contact of saidthird relay connected in series with said series circuit; and whereinsaid retention unit comprises: a second normally open contact of saidthird relay connected in series with said primary contact of saidleft-hand push-button switch in said first or second parallel circuit,thus serving to conduct the coil of said first relay; a third normallyopen contact of said third relay connected in series with said primarycontact of said right-hand push-button switch in said first or secondparallel circuit, thus serving to conduct the coil of said second relay;and a fourth normally open contact of said third relay connected inseries with said second or first parallel circuit, not serving toconduct the coil of said first nor second relay.
 5. The enabler forteaching pendant as claimed in claim 1, wherein said both push-buttonswitches each comprise, as said auxiliary contact, a first auxiliarycontact which is closed when said both primary contacts are in saidfirst OFF state and which is opened in said ON state and in said secondOFF state, and a second auxiliary contact which is closed when said bothprimary contacts are in said first OFF state and in said ON state andwhich is opened in said second OFF state; wherein said at least oneprimary contact of said left-hand push-button switch is connected inparallel with said at least one primary contact of said right-handpush-button switch to form a parallel circuit; wherein said firstauxiliary contact of said left-hand push-button switch is connected inseries with said first auxiliary contact of said right-hand push-buttonswitch to form a first series circuit; wherein said second auxiliarycontact of said left-hand push-button switch is connected in series withsaid second auxiliary contact of said right-hand push-button switch toform a second series circuit; and wherein said inhibition meanscomprises: a detection unit for detecting an open or close state of saidparallel circuit and an open or close state of said first or secondseries circuit; and a retention unit for retaining said parallel circuitin the open state for a period of time between when said detection unitdetects the open state of said parallel circuit and the open state ofsaid second series circuit, and when said detection unit detects theopen state of said parallel circuit and the close state of said firstseries circuit.
 6. The enabler for teaching pendant as claimed in claim1, wherein said both push-button switches each comprise, as saidauxiliary contact, a first auxiliary contact which is closed when saidboth primary contacts are in said first OFF state and which is opened insaid ON state and in said second OFF state, and a second auxiliarycontact which is closed when said both primary contacts are in saidfirst OFF state and in said ON state and which is opened in said secondOFF state, wherein said at least one primary contact of said left-handpush-button switch is connected in parallel with said at least oneprimary contact of said right-hand push-button switch to form a parallelcircuit; wherein said first auxiliary contact of said left-handpush-button switch is connected in series with said first auxiliarycontact of said right-hand push-button switch to form a first seriescircuit; wherein said second auxiliary contact of said left-handpush-button switch is connected in series with said second auxiliarycontact of said right-hand push-button switch to form a second seriescircuit which is connected in parallel with said first series circuit,and wherein said inhibition means comprises: a fourth relay, a coil ofwhich is electrically energized by switching ON said both auxiliarycontacts in said first series circuit; a first normally open contact ofsaid fourth relay connected in series with said second series circuit;and a second normally open contact of said fourth relay connected inseries with said parallel circuit.
 7. The enabler for teaching pendantas claimed in claim 1, wherein said both push-button switches eachcomprise, as said auxiliary contact, a first auxiliary contact which isclosed when said both primary contacts are in said first OFF state andwhich is opened in said ON state and in said second OFF state, and asecond auxiliary contact which is closed when said both primary contactsare in said first OFF state and in said ON state and which is opened insaid second OFF state; wherein said at least one primary contact of saidleft-hand push-button switch is connected in parallel with said at leastone primary contact of said right-hand push-button switch to form aparallel circuit; wherein said first auxiliary contact of said left-handpush-button switch is connected in series with said first auxiliarycontact of said right-hand push-button switch to form a first seriescircuit; wherein said second auxiliary contact of said left-handpush-button switch is connected in series with said second auxiliarycontact of said right-hand push-button switch to form a second seriescircuit which is connected in parallel with said first series circuit;wherein said inhibition means comprises: a fifth relay, a coil of whichis electrically energized by switching ON said both auxiliary contactsin said first series circuit; and a normally open contact of said fifthrelay connected in series with said second series circuit, and whereinsaid parallel circuit is connected in series with said first seriescircuit.
 8. The enabler for teaching pendant as claimed in claim 1,wherein said both push-button switches each comprise, as said auxiliarycontact, a first auxiliary contact which is closed when said bothprimary contacts are in said first OFF state and which is opened in saidON state and in said second OFF state, and a second auxiliary contactwhich is closed when said both primary contacts are in said first OFFstate and in said ON state and which is opened in said second OFF state;wherein said at least one primary contact of said left-hand push-buttonswitch is connected in parallel with said at least one primary contactof said right-hand push-button switch to form a parallel circuit;wherein said first auxiliary contact of said left-hand push-buttonswitch is connected in series with said first auxiliary contact of saidright-hand push-button switch to form a first series circuit; whereinsaid second auxiliary contact of said left-hand push-button switch isconnected in series with the second auxiliary contact of said right-handpush-button switch to form a second series circuit; wherein saidinhibition means comprises a sixth relay including a normally opencontact and a c-contact, and a seventh relay including a normally opencontact and a c-contact; wherein said normally open contact of saidsixth relay and said normally open contact of said seventh relay areconnected in series with said parallel circuit; wherein a normally closeterminal of said c-contact of said sixth relay and a normally closeterminal of said c-contact of said seventh relay are connected toopposite ends of said first series circuit; and wherein a normally openterminal of said c-contact of said sixth relay and a normally openterminal of said c-contact of said seventh relay are connected toopposite ends of said second series circuit.
 9. The enabler for teachingpendant as claimed in claim 1, wherein said left-hand and saidright-hand push-button switches include two of said primary contacts,respectively; wherein said both push-button switches each comprise, assaid auxiliary contact, a first auxiliary contact which is closed whensaid both primary contacts are in said first OFF state and which isopened in said ON state and in said second OFF state, and a secondauxiliary contact which is closed when said both primary contacts are insaid first OFF state and in said ON state and which is opened in saidsecond OFF state; wherein one of said primary contacts of said left-handpush-button switch is connected in parallel with one of said primarycontacts of said right-hand push-button switch to form a first parallelcircuit; wherein the other of said primary contacts of said left-handpush-button switch is connected in parallel with the other of saidprimary contacts of said right-hand push-button switch to form a secondparallel circuit; wherein said first auxiliary contact of said left-handpush-button switch is connected in series with said first auxiliarycontact of said right-hand push-button switch to form a first seriescircuit; wherein said second auxiliary contact of said left-handpush-button switch is connected in series with said second auxiliarycontact of said right-hand push-button switch to form a second seriescircuit; wherein said inhibition means comprises an eighth relayincluding a normally open contact and a c-contact, and a ninth relayincluding a normally open contact and a c-contact; wherein either one ofsaid normally open contact of said eighth relay and said normally opencontact of said ninth relay is connected in series with said firstparallel circuit; wherein the remaining normally open contact of saideighth or ninth relay is connected in series with said second parallelcircuit; wherein a normally close terminal of said c-contact of saideighth relay and a normally close terminal of said c-contact of saidninth relay are connected to opposite ends of said first series circuit;and wherein a normally open terminal of said c-contact of said eighthrelay and a normally open terminal of said c-contact of said ninth relayare connected to opposite ends of said second series circuit.
 10. Theenabler for teaching pendant as claimed in claim 1, wherein said bothpush-button switches each comprise, as said auxiliary contact, a firstauxiliary contact which is closed when said both primary contacts are insaid first OFF state and which is opened in said ON state and in saidsecond OFF state, and a second auxiliary contact which is closed whensaid both primary contacts are in said first OFF state and in said ONstate and which is opened in said second OFF state; wherein said atleast one primary contact of said left-hand push-button switch isconnected in parallel with said at least one primary contact of saidright-hand push-button switch to form a parallel circuit; wherein saidfirst auxiliary contact of said left-hand push-button switch isconnected in series with said first auxiliary contact of said right-handpush-button switch to form a first series circuit; wherein said secondauxiliary contact of said left-hand push-button switch is connected inseries with said second auxiliary contact of said right-hand push-buttonswitch to form a second series circuit; wherein said inhibition meanscomprises a tenth relay including a first and a second normally opencontact and a normally close contact, said second normally open contactand said normally close contact of which are simultaneously switched,and an eleventh relay including a first and a second normally opencontact and a normally close contact, said second normally open contactand said normally close contact of which are simultaneously switched;wherein said first normally open contact of said tenth relay and saidfirst normally open contact of said eleventh relay are connected inseries with said parallel circuit; wherein said normally close contactof said tenth relay and said normally close contact of said eleventhrelay are connected in series with said first series circuit; andwherein said second normally open contact of said tenth relay and saidsecond normally open contact of said eleventh relay are connected inseries with said second series circuit.
 11. The enabler for teachingpendant as claimed in claim 1, wherein said left-hand and saidright-hand push-button switches include two of said primary contacts,respectively; wherein said both push-button switches each comprise, assaid auxiliary contact, a first auxiliary contact which is closed whensaid both primary contacts are in said first OFF state and which isopened in said ON state and in said second OFF state, and a secondauxiliary contact which is closed when said both primary contacts are insaid first OFF state and in said ON state and which is opened in saidsecond OFF state; wherein one of said primary contacts of said left-handpush-button switch is connected in parallel with one of said primarycontacts of said right-hand push-button switch to form a first parallelcircuit; wherein the other of said primary contacts of said left-handpush-button switch is connected in parallel with the other of saidprimary contacts of said right-hand push-button switch to form a secondparallel circuit; wherein said first auxiliary contact of said left-handpush-button switch is connected in series with said first auxiliarycontact of said right-hand push-button switch to form a first seriescircuit; wherein said second auxiliary contact of said left-handpush-button switch is connected in series with said second auxiliarycontact of said right-hand push-button switch to form a second seriescircuit; wherein said inhibition means comprises a twelfth relayincluding a first and a second normally open contact and a normallyclose contact, said second normally open contact and said normally closecontact of which are simultaneously switched, and a thirteenth relayincluding a first and a second normally open contact and a normallyclose contact, said second normally open contact and said normally closecontact of which are simultaneously switched; wherein either one of saidfirst normally open contact of said twelfth relay and said firstnormally open contact of said thirteenth relay is connected in serieswith said first parallel circuit; wherein the remaining first normallyopen contact of said twelfth or thirteenth relay is connected in serieswith said second parallel circuit; wherein said normally close contactof said twelfth relay and said normally close contact of said thirteenthrelay are connected in series with said first series circuit; andwherein said second normally open contact of said twelfth relay and saidsecond normally open contact of said thirteenth relay are connected inseries with said second series circuit.
 12. The enabler for teachingpendant as claimed in any one of claims 3, 4 and 6 to 11, wherein saidrelays are disposed on a circuit substrate in said pendant body.
 13. Theenabler for teaching pendant as claimed in claim 2 or 5, wherein saiddetection unit is disposed on a circuit substrate in said pendant body.14. The enabler for teaching pendant as claimed in any one of claims 3,4 and 6 to 11, wherein said relays are disposed in said switch case ofsaid left-hand or right-hand push-button switch.
 15. The enabler forteaching pendant as claimed in claim 2 or 5, wherein said detection unitis disposed in said switch case of said left-hand or right-handpush-button switch.
 16. The enabler for teaching pendant as claimed inany one of claims 3, 4 and 6 to 11, wherein said relays are disposed ina relay box provided externally of said pendant body.
 17. The enablerfor teaching pendant as claimed in claim 2 or 5, wherein said detectionunit is disposed in a relay box provided externally of said pendantbody.